Disk drive data storage capabilities are being continuously enhanced by both the ability to store data more compactly at higher densities and by progressively lowering the cost per megabyte. Demand for storage continues to grow with the introduction of computer applications with more substantial storage requirements and can be expected to experience an acceleration of growth as cost effectiveness increases permit the use for further applications with high storage requirements.
Among the recording techniques used to enhance the utilization of the media storage surface, the most common is zone recording wherein data is stored in bands of concentric tracks with recording occurring at a constant frequency. The innermost track of a band or track with the smallest diameter is recorded at the maximum density and all other tracks on the surface or within the band are recorded at less than the optimum linear density. Zone recording allows a linear density defined by the innermost track of the band or zone which reduces the disparity between the recording density of the tracks and enhances the the usable storage capacity of the disk or the disk drive of which it is a part.
The zone recording may be further fine tuned by optimizing the frequency or recording density for each head disk interface with respect to each zone. Such a technique is shown in U.S. Pat. No. 5,087,992 wherein the frequency is set within each zone to the maximum error rate that does not exceed a selected value. Another approach is taught in U.S. Pat. No. 4,799,112 wherein the frequency is optimized for each track of the disk in accordance with the characteristics of the head disk interface. U.S. Pat. No. 4,604,748 teaches the recording of different types of data which have differing error tolerances. For that data which is more sensitive to errors, dual recording is used and also a higher level of error recovery is applied.